高原反应吃什么药十字文明用语LT1931LT1931A PARAMETER
CONDITIONS
MIN
TYP MAX MIN TYP MAX上海周末
UNITS
Minimum Operating Voltage 2.45
2.6 2.45
2.6V Maximum Operating Voltage 16
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16
V Feedback Voltage
–1.275–1.255–1.235–1.275–1.255–1.235V q
–1.280–1.230
–1.280–1.230
V NFB Pin Bias Current V NFB = –1.255V
q
48816µA Quiescent Current
V SHDN = 2.4V, Not Switching 4.26 5.88mA Quiescent Current in Shutdown V SHDN = 0V, V IN = 3V 0.0110.011µA Reference Line Regulation 2.6V ≤ V IN ≤ 16V
梨花劫0.01
0.050.01
0.05%/V Switching Frequency
1 1.
2 1.4 1.8 2.2 2.6MHz q 0.85 1.6
1.6
2.9
MHz Maximum Duty Cycle q
84907582%Switch Current Limit (Note 3)1
1.221
1.2
2.5A Switch V CESAT
I SW = 1A 400600400600mV Switch Leakage Current V SW = 5V
0.01
10.01
1µA SHDN Input Voltage, High 2.4
2.4
V SHDN Input Voltage, Low 0.5
0.5
V SHDN Pin Bias Current
V SHDN = 3V 16323570µA V SHDN = 0V 0
0.10
0.1µA
T JMAX = 125°C, θJA = 256°C/W
ORDER PART NUMBER (Note 1)
蔚什么什么风V IN Voltage ..............................................................16V –0.4V to 36V –2V Current Into . ±1mA .16V Maxim
um 125°C Operating Temperature Range (Note 2)..–40°C to 85°C Storage –65°C to 150°C Lead Temperature (Soldering, 10 c)..................300°C
LT1931ES5LT1931AES5ABSOLUTE AXI U RATI GS
W W W
U PACKAGE/ORDER I FOR ATIO
U U W
The q denotes specifications which apply over the full operating temperature range, otherwi specifications are T A = 25°C.V IN = 3V, V SHDN = V IN , unless otherwi noted. (Note 2)
SW 1GND 2TOP VIEW
S5 PACKAGE
5-LEAD PLASTIC SOT-23NFB 3
5 V IN
晋人好利4 SHDN S
5 PART MARKING
LTRA LTSP
ELECTRICAL CHARACTERISTICS
Note 1: Absolute Maximum Ratings are tho values beyond which the life of a device may be impaired.
Note 2: The LT1931E/LT1931AE are guaranteed to meet performance specifications from 0°C to 70°C. Specifications over the –40°C to 85°C
operating temperature range are assured by design, characterization and correlation with statistical process controls.
Note 3: Current limit guaranteed by design and/or correlation to static test.
Consult factory for parts specified with wider operating temperature ranges.
APPLICATIO S I FOR ATIO
W U
U
U LT1931A AND LT1931 DIFFERENCES:Switching Frequency
The key difference between the LT1931A and LT1931 is the faster switching frequency of the LT1931A. At 2.2MHz,the LT1931A switches at nearly twice the rate of the LT1931. Care must be taken in deciding which part to u.The high switching frequency of the LT1931A allows smaller cheaper inductors and capacitors to be ud in a given application, but with a slight decrea in efficiency and maximum output current when compared to the LT1931. Generally, if efficiency and maximum output current are critical, the LT1931 should be ud. If applica-tion size and cost are more important, the LT1931A will be the better choice. In many applications, tiny inexpensive chip inductors can be ud with the LT1931A, reducing solution cost.Duty Cycle
The maximum duty cycle (DC) of the LT1931A is 75%compared to 84% for the LT1931. The duty cycle for a given application using the dual inductor inverting topol-ogy is given by:DC V V V OUT IN OUT =
+||||||
For a 5V to –5V application, the DC is 50% indicating that the LT1931A can be ud. A 5V to –16V application has a DC of 76.2% making the LT1931 the right choice. The LT1931A can still be ud in applications where the DC, as calculated above, is above 75%. However, the part must be operated in the discontinuous conduction mode so that the actual duty cycle is reduced.INDUCTOR SELECTION
Several inductors that work well with the LT1931 are listed in Table 1 and tho for the LT1931A are listed in Table 2.Besides the, there are many other inductors that can be ud. Consult each manufacturer for detailed information and for their entire lection of related parts. Ferrite core inductors should be ud to obtain the best efficiency, as
core loss at frequencies above 1MHz are much lower for ferrite cores than for powdered-iron units. When using coupled inductors, choo one that can handle at least 1A of current without saturating, and ensure that the inductor has a low DCR (copper-wire resistance) to minimize I 2R power loss. If using uncoupled inductors, each inductor need only handle one-half of the total switch current so that 0.5A per inductor is sufficient. A 4.7µH to 15µH coupled inductor or a 15µH to
22µH uncoupled inductor will usually be the best choice for most LT1931 designs.For the LT1931A, a 2.2µH to 4.7µH coupled inductor or a 3.3µH to 10µH uncoupled inductor will usually suffice. In certain applications such as the “Charge Pump” inverting DC/DC converter, only a single inductor is ud. In this ca, the inductor must carry the entire 1A switch current.
Table 1. Recommended Inductors—LT1931
L Size
PART (µH)(L × W × H) mm VENDOR CLS62-10010 6.8 × 6.6 × 2.5Sumida
CR43-15015 4.5 × 4.0 × 3.2(847) CTX10-1108.9 × 11.4 × 4.2
Coiltronics CTX15-115(407) 241-7876
www. LQH3C100K2410 3.2 × 2.5 × 2.0
Murata
LQH4C150K04
15
(404)
Table 2. Recommended Inductors—LT1931A
L Size
PART (µH)(L × W × H) mm VENDOR
ELJPC3R3MF 3.3 2.5 × 2.0 × 1.6
Panasonic
ELJPC4R7MF 4.7(408) CLQ4D10-4R71 4.77.6 × 4.8 × 1.8
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Sumida
CLQ4D10-6R82 6.8(847) LB20164R7M 4.7 2.0 × 1.6 × 1.6
Taiyo Yuden LB20163R3M 3.3(408) LQH3C4R7K24 4.7 3.2 × 2.5 × 2.0
Murata
LQH4C100K24
10
(404)
1U drawing #5382-T0392U drawing #5382-T041
